Having won her fourth title of the season last week in Stanford, this week's progress continued Williams' recovery since withdrawing from Wimbledon because of equilibrium problems.

“I served great,” said Williams, celebrating her 200th week at No. 1 in the world. “I needed to serve great because she was hitting unbelievable serves to me.”

Williams has won the Rogers Cup three times when it is held on alternate years in Toronto, including last year, but she had not played in Montreal since she retired from the final with an injury in 2000.

In the quarterfinals Friday, Williams will play Caroline Wozniacki, a 6-1, 6-0 winner over American qualifier Shelby Rogers.

“I felt really comfortable and confident,” Wozniacki said. “I served and returned well. She's a tough player. She has some big shots. I was just able to neutralize them and play my game.”

The 11th-seeded Wozniacki, coming off a victory in Istanbul, has dropped only six games in three matches this week.

“It will be a great match,” said Williams, 6-1 against Wozniacki. “She's playing great tennis. She's really focused. It will be a good match to see where I am.”